In recent years, various nanowire-based devices have emerged with many potentially useful applications. Nanowires are wire-like structures that typically have diameters of less that about 100 nanometers and can be used as an electrical interconnection between electronic devices and in numerous other applications. One method of forming nanowires is the vapor-liquid-solid (“VLS”) chemical synthesis process. Generally, this method involves depositing particles of a catalyst material such as gold or titanium on a surface of a structure on which it is desired to grow nanowires. The structure is placed in a chamber and heated to temperatures typically ranging between about 250° C. to about 1000° C. Precursor gasses including elements or compounds that will be used to form the nanowires are introduced into the chamber. The particles of the catalyst material cause the precursor gasses to at least partially decompose into their respective elements, some of which are transported on or through the particles of catalyst material and deposited on the underlying surface. As this process continues, nanowires are grown with the catalyst particle remaining on the tip or end of the nanowires. Nanowires can also be formed by physical vapor deposition or by surface atom migration.
During nanowire formation, the elements or compounds selected to form the nanowires can be varied. These nanowires are referred to as “heterostructure nanowires.” In particular, a nanowire having a composition that varies along the longitudinal length of the nanowire is referred to as a “longitudinal heterostructure nanowire,” and a nanowire having a radially varying composition is referred to as “coaxial heterostructure nanowire.” Different regions or segments of these heterostructure nanowires can also be doped with electron donating and electron accepting impurities to form various semiconductor devices within the nanowires, such as p-n, p-i-n, p-n-p, and n-p-n junctions that can be used as diodes or field-effect transistors. However, implementing heterostructure nanowires in devices that can be employed in a wide range of other potentially useful applications remains a challenge.